A. Gallifuoco et al., ON THE USE OF CHITOSAN-IMMOBILIZED BETA-GLUCOSIDASE IN WINE-MAKING - KINETICS AND ENZYME-INHIBITION, Process biochemistry, 33(2), 1998, pp. 163-168
The kinetics of chitosan-immobilized beta-glucosidase and enzyme inhib
ition by several components of wine and must (glucose, fructose and te
rpenols) were studied. Optimum immobilization conditions were: tempera
ture 25 degrees C, pH between 5.5 and 6.0, polymeric support dimension
in the range 38-75 mu m, cross-linking time 30 min, glutaraldehyde co
ncentration 0.5-1.0% w/v, 1 g of chitosan per 1000 units of beta-gluco
sidase. The immobilized enzyme retained 29% of the wet biocatalyst act
ivity when freeze-dried and showed good stability (half-life roughly 2
years) when stored at 4 degrees C. Kinetics were tested at 25 degrees
C following the hydrolysis of beta-nitrophenyl beta-D glucopyranoside
and obey the Michaelis-Menten rate equation. K-m = 1.3 mM and the act
ivation energy, 62.84 kJ mol(-1), are close to those of the free enzym
e. The operational half-life was roughly 500 h. Glucose only depressed
the enzyme activity according to a reversible non-competitive inhibit
ion mechanism with K-i = 11.2 mM.